The present invention relates to generally a method for manufacturing color-picture tubes, and more particularly a method for exposing a photosensitive layer uniformly coated upon the inner surface of the faceplate of the picture tube so as to form a desired phosphor dot pattern or the like.
In the step of exposing a photosensitive layer uniformly deposited upon the inner surface of the faceplate of a color-picture tube so as to form a desired phosphor screen pattern, a desired spot is exposed by the light beam emitted from a point light source located at one of the centers of deflection and projected through an optical correction lens system and a shadow mask. Thereafter, the exposed layer is developed so that the phosphor or temporary dots or stripes may be formed.
The optical correction lens system interposed between the light source and the shadow mask consists of a single or a plurality of correction lenses with a complicated aspherical surface so that the light beam may precisely impinge at a point where the corresponding electron beam impinges. To form the phosphor screen of a color-picture tube of the type with a wide deflection angle such as with a 110.degree. deflection angle, a very complex optical correction lens system is required, and it is very difficult to manufacture aspherical correction lenses having such a complicated surface.